The invention relates to the production of socks with a thread mesh relatively larger than that of women's stockings and to the problem of tensioning the manufactured articles and reversing them after each manufactured article has been formed. There are in existence pneumatic tensioning and reversing devices for tubular manufactured articles such as stockings and the like, reversing being performed upon completion by the circular knitting machine with a rotating-needle cylinder. Devices of this type have an external tubular casing and a rotating internal tube; an interspace with an annular cross section is thus defined, this interspace being used for pneumatic tensioning--by means of suction--of the manufactured article which during formation surrounds the internal tube (which therefore must rotate); after the manufactured article has been separated from the needle cylinder used for its production, the airflow is reversed so as to cause a sucking action inside the rotating tubular duct and advantageously also a pneumatic thrusting action on the manufactured article which surrounds the said rotating tube and which is located in the interspace; this arrangement results in inward turning and hence reversal of the manufactured article, from the external interspace with an annular cross section into the internal tube, the reversed manufactured article being pneumatically conveyed away through a pneumatic duct of which the said rotating internal tube forms part.
Devices of this kind are difficult to apply in circular knitting machines and the like, of the type for forming socks, where the manufactured article is relatively large and the needle cylinder has a relatively small diameter, it being extremely difficult to arrange inside the needle cylinder both the external tubular casing and the rotating internal tube so as to be able to perform the operations of tensioning and in particular reversing the manufactured article within the internal tube, the latter having too small a diameter for the inward turning operation and hence reversal to be performed properly.
The device in question has been designed in order to solve this problem in machines which have a cylinder with a relatively small diameter.
The device in question is an improvement to that indicated above, with an annular interspace from which the manufactured article is turned inward and reversed during an operation where the said article is reversed and pneumatically conveyed away. According to the invention, both the said tubular casing and an internal element--which is at least partly tubular--consist of two sections with different diameters, the upper sections with a smaller diameter being accommodated within the needle cylinder, while the lower sections with a larger diameter are located outside and adjacent to the needle cylinder; means are provided for forming an annular discontinuity between the two sections of the said internal element so that, after a first phase involving formation with pneumatic tensioning, a second phase involving inward turning and reversal can be performed along the end edge of the tubular section of the internal element with a larger diameter, and within the said section.
In practice, the section of said internal element with a smaller diameter is joined to an enlargement so as to have a diameter at least equal to that of the tubular section of said internal element with a larger diameter.
The sections of the internal element are movable axially relative to each other so as to create the said annular discontinuity during the reversal phase. In a possible embodiment, the tubular section of the internal element with a larger diameter can be displaced axially so as to move towards and away from the said enlargement, in order to form the said annular discontinuity during the reversal phase.
Advantageously, the enlargement of the section of the internal element with a smaller diameter can be engaged into (and disengaged from) the end of the tubular section of the internal element with a larger diameter, which thus supports--during the tensioning phase--the said section with a smaller diameter; in addition, provision is made for slide means with jaws or the like, which from the outside are moved across the interspace with an annular cross section so as to engage temporarily the said section of the internal element with a smaller diameter at the end of the tensioning phase--after the manufactured article has been separated from the needles--and during the reversal phase. Said means with jaws or the like may engage said section of the internal element with a smaller diameter via ball bearing means so as to allow rotation.
The tubular section of the internal element with a larger diameter may be rotational and capable of rotating with the said upper section of said internal element with a smaller diameter; said tubular section with a larger diameter may be driven, i.e. operated in rotation, or may be free to rotate, and in this latter case may be combined with an air-type propulsion system which uses the suction airflow prevailing inside the annular interspace for tensioning.
In a different embodiment, the section of said internal element with a smaller diameter may be driven in rotation by the plate; it may be capable of being coupled with the plate via a friction joint with axial pressure or the like.
Also, in another embodiment, the enlargement of the section of the internal element with a smaller diameter has rolling bearing means or the like for engagement with the tubular section.
Moreover, the section of the internal element with a smaller diameter may be tubular and, via said section and the section of said internal element with a larger diameter, there may be created a pneumatic thrusting force, from the end in the interspace, in the same direction as the tensioning airflow for suction, said thrusting force tending also to widen the manufactured article.
According to yet another solution, said section with a smaller diameter, together with the corresponding enlargement of the internal element, is mounted on a rod passing axially through the rotating structure of the plate and driven rotatably by it, and, via said rod, the said section of the internal element with a smaller diameter is operated axially so as to move towards and away from the tubular section with a larger diameter, which may be fixed.
According to another embodiment, the upper section of the internal element is formed as a rod which is suspended from the hook plate and is able to lift therewith; means are advantageously provided to ensure the centering of the lower enlargement of the rod over the lower tubular section of the internal element with a larger diameter, even upon the mutual moving away.
The lower enlargement of the rod--mostly having a dual truncated cone shape--may have a thin appendix which remains centered within the upper opening of the lower section of the internal element with a larger diameter, even after the enlargement and the lower section have been mutually moved apart in order to form the annular discontinuity for the reversing operation.
The rod may be hinged to the plate, or may be at least partially flexible, to allow the lifting of the plate about a hinge having horizontal axis, i.e. with an angular movement.
According to a further improvement, air inlet holes are also provided as well as means for controlling the opening and closing thereof, in order to reduce the speed of the air which flows through the section of the casing which is inside the needle cylinder and closer to the working zone of the needles.
Said holes may be formed around the upper portion of the external section with a larger diameter of the casing, and around the latter there may be provided a sliding sleeve shutter operable by the program which controls the machine.
Advantageously, below the set of holes, a slotting may be provided for access to the inside of the tubular casing; said slotting may be closed by the sleeve shutter and opened by an extra-run of the latter to gain access inside the device.
An annular shaped structure which is adjustable in position to regulate the air flow may be provided inside the section with a larger diameter of the casing. A grid which is adjustable in position in order to intercept the article and position it as suitably as possible for its reversing may be provided within the interspace between the two sections with a larger diameter.
The upper section of the internal element with a smaller diameter may be designed in the form of a rod having an enlargement at its lower end, which is idly supported on said rod.